Diffusion-based electrochemical sensor

Abstract

A target molecule detection method includes contacting an oxidation electrode and a reduction electrode with a solution having a redox tag. The method further includes applying a first oxidation voltage pulse to the oxidation electrode when the solution does not contain the target molecule to obtain a first oxidation current curve, applying a second oxidation voltage pulse to the oxidation electrode when the solution contains the target molecule to obtain a second oxidation current curve, a first reduction voltage pulse is applied to the reduction electrode when the solution does not contain the target molecule to obtain a first reduction current curve, and a second reduction voltage pulse is applied to the reduction electrode when the solution contains the target molecule to obtain a second reduction current curve. The method further includes detecting the target molecule in response to one or more electrical properties of the first and second oxidation and reduction current profiles.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to diffusion-based electrochemical sensors. The invention includes embodiments relating to diffusion-based electrochemical sensor systems and sensing methods that utilize the diffusion mechanism of a target molecule binding between an oxidizing electrode and a reducing electrode. BACKGROUND

[0002] Diffusion is a physical process that reflects the random movement of molecules in a fluid with a concentration gradient. The rate of diffusion of a molecule can depend on the mass of the molecule, the amount of thermal energy of the molecule, and / or environmental factors, such as temperature and / or viscosity. Generally, heavier molecules move slower than lighter molecules by diffusion. Two molecules bind together to form a binding complex. Relatively, the binding complex moves slower than when the two molecules are separated. Diffusion mechanisms have been used for electrochemical detection of redox molecules in solution. SUMMARY

[0003] According to one embodiment, an electrochemical sensor system based on target molecule diffusion is disclosed. The electrochemical sensor system based on target molecule diffusion includes a chamber configured to hold a solution having a redox tag and a capture agent bound to the redox tag. The redox tag exists in the solution in a reduced state and / or an oxidized state. The capture agent is configured to bind to a target molecule introduced into the solution. The target molecule detection system further includes an oxidation electrode configured to oxidize the redox tag existing in the reduced state in the solution to the oxidized state. When the solution does not contain the target molecule, the oxidation electrode is configured to output a first oxidation current profile in response to a first oxidation voltage pulse applied to the oxidation electrode. When the solution contains the target molecule, the oxidation electrode is configured to output a second oxidation current profile in response to a second oxidation voltage pulse applied to the oxidation electrode. The electrochemical sensor system based on target molecule diffusion further includes a reduction electrode spaced apart from the oxidation electrode and configured to reduce the redox tag existing in the oxidized state in the solution to the reduced state. When the solution does not contain the target molecule, the reduction electrode is configured to output a first reduction current profile in response to a first reduction voltage pulse applied to the reduction electrode. When the solution contains the target molecule, the reduction electrode is configured to output a second reduction current profile in response to a second reduction voltage pulse applied to the reduction electrode. One or more electrical properties of the first and second oxidation current profiles and the first and second reduction current profiles indicate the presence of the target molecule. The initial state of the redox tag can depend on the specific characteristics of the redox tag. If the redox tag is stable in the reduced state, then the initial state is only the reduced state, and vice versa. If the initial stable state of the redox tag is in the reduced state, then the signaling process starts from the oxidation electrode. If the initial stable state of the redox tag is in the oxidized state, then the signaling process starts from the reduction electrode.

[0004] In another embodiment, an electrochemical sensing method based on diffusion of a target molecule is disclosed. The method includes contacting an oxidation electrode and a reduction electrode with a solution having a redox tag and a capture agent bound to the redox tag. The redox tag exists in the solution in a reduced state and / or an oxidized state. The capture agent is configured to bind to a target molecule introduced into the solution. The method further includes applying a first oxidation voltage pulse to the oxidation electrode to obtain a first oxidation current profile when the solution does not contain the target molecule, applying a second oxidation voltage pulse to the oxidation electrode to obtain a second oxidation current profile when the solution contains the target molecule, applying a first reduction voltage pulse to the reduction electrode to obtain a first reduction current profile when the solution does not contain the target molecule, and applying a second reduction voltage pulse to the reduction electrode to obtain a second reduction current profile when the solution contains the target molecule. The method also includes detecting the target molecule in response to one or more electrical properties of the first and second oxidation current profiles and the first and second reduction current profiles. The initial state of the redox tag can depend on the specific properties of the redox tag. If the redox tag is stable in the reduced state, then the initial state is only the reduced state, and vice versa. If the initial stable state of the redox tag is in the reduced state, then the signaling process starts from the oxidation electrode. If the initial stable state of the redox tag is in the oxidized state, then the signaling process starts from the reduction electrode.

[0005] In another embodiment, an electrochemical sensing method based on diffusion of a target molecule is disclosed. The method includes contacting an oxidation electrode and a reduction electrode with a solution having a redox tag and a capture agent bound to the redox tag. The redox tag exists in the solution in a reduced state and / or an oxidized state. The capture agent is configured to bind to a target molecule introduced into the solution. The method further includes applying a first oxidation voltage pulse to the oxidation electrode to obtain a first oxidation current profile when the solution does not contain the target molecule, applying a second oxidation voltage pulse to the oxidation electrode to obtain a second oxidation current profile when the solution contains the target molecule, applying a first reduction voltage pulse to the reduction electrode to obtain a first reduction current profile when the solution does not contain the target molecule, and applying a second reduction voltage pulse to the reduction electrode to obtain a second reduction current profile when the solution contains the target molecule. The method also includes detecting the target molecule in response to one or more electrical properties of the first and second oxidation current profiles and the first and second reduction current profiles. The initial state of the redox tag can depend on the specific properties of the redox tag. If the redox tag is stable in the reduced state, then the initial state is only the reduced state, and vice versa. If the initial stable state of the redox tag is in the reduced state, then the signaling process starts from the oxidation electrode. If the initial stable state of the redox tag is in the oxidized state, then the signaling process starts from the reduction electrode. BRIEF DESCRIPTION OF DRAWINGS

[0006] Figure 1 A schematic diagram of an electrochemical detection system with an oxidation electrode, a reduction electrode, and a passivation layer is depicted.

[0007] Figure 2A A schematic diagram of the reaction and diffusion mechanism of a redox tag in an electrochemical detection system is depicted. Figure 1

[0008] Figure 2B A plot of an oxidation voltage pulse applied to the oxidation electrode (Ml) and the oxidation potential of the oxidation electrode is depicted.

[0009] Figure 2C A plot of a reduction voltage pulse applied to the reduction electrode (M2) and the reduction potential of the reduction electrode is depicted.

[0010] Figure 2D A plot of an oxidation current curve at the oxidation electrode in response to the oxidation voltage pulse shown in Figure 2B

[0011] Figure 2E A plot of a reduction current curve at the reduction electrode in response to the reduction voltage pulse shown in Figure 2C

[0012] Figure 3A A schematic diagram of the reaction and diffusion mechanism of a redox tag in an electrochemical detection system is depicted, wherein a target molecule is added to the solution.

[0013] Figure 3B A plot of an oxidation voltage pulse applied to the oxidation electrode (Ml) and the oxidation potential of the oxidation electrode is depicted.

[0014] Figure 3C A plot of a reduction voltage pulse applied to the reduction electrode and the reduction potential curve of the reduction electrode is depicted.

[0015] Figure 3D A plot of an oxidation current curve at the oxidation electrode in response to the oxidation voltage pulse in Figure 3B

[0016] Figure 3E A plot of a reduction current curve at the reduction electrode in response to the reduction voltage pulse in Figure 3C

[0017] Figure 4A A schematic diagram of an electrochemical detection system is depicted, the system comprising a microchannel, the microchannel being partially closed by a first valve and a second valve connected thereto.

[0018] Figure 4B ​​​​​A schematic perspective view of an electrochemical detection system including a base and an array of microwells extending into the base is depicted.

[0019] Figure 4C An enlarged, isolated perspective view of a microwell in the array of microwells is depicted. DETAILED DESCRIPTION

[0020] Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and that other embodiments can take various and alternative forms. The figures are not necessarily to scale; some features can be exaggerated or minimized for the purpose of clarity. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present embodiments. As those skilled in the art will appreciate, the various features illustrated and described in connection with any one of the figures can be combined with features illustrated and described in connection with one or more other figures, and the combination of various

[0021] Except in the examples, or where otherwise expressly indicated, all numerical quantities in this description specifying amounts of materials and / or conditions and / or use of conditions are to be understood as modified by the word "about" in describing the broadest range of embodiments. Unless otherwise stated, the preferred values in a given range are more preferred. Also, all ranges include any and all sub-ranges subsumed therein. It is to be understood that such terms as "including," "comprising," "consisting" and "consisting essentially of" of the specification are open-ended and do not exclude the use of other

[0022] The first definition of a first letter abbreviation or other abbreviation applies to all subsequent uses of that same abbreviation herein and is intended to apply equally to grammatical variations of the originally defined abbreviation. Unless expressly stated to the contrary, a measurement of a property is determined by the same technique referred to earlier or later in the specification for the same property.

[0023] It must also be noted that, as used in the specification and the appended claims, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise. For example, reference to a component can include a plurality of components.

[0024] The terms "substantially," "about," or "approximately" as used herein mean an amount that is acceptable, within manufacturing tolerances, or within a range that is acceptable for the specified value or within a range that is acceptable for the specified value. These terms can be used to modify any numerical value disclosed or claimed herein. Generally, the term "about" when used in reference to a particular value indicates a range of ± 5% of that value. As an example, the phrase "about 100" refers to a range of 100 ± 5, i.e., a range of 95 to 105. Generally, when the term "about" is used, it is contemplated that similar results or effects can be obtained within a range of ± 5% of the indicated value according to the application. The term "substantially" can modify a value or relative characteristic disclosed or claimed in the present disclosure. In such cases, "substantially" can mean that the value or relative characteristic it modifies is within ± 0%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, or 10% of that value or relative characteristic.

[0025] It should also be understood that an integer range expressly includes all integers within that range. For example, an integer range 1 to 10 expressly includes 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Similarly, a range 1 to 100 includes 1, 2, 3, 4.... 97, 98, 99, 100. Similarly, when any range is called for, intermediate numbers intermediate of the upper and lower limits of a range based on the increments of 10 can be taken as alternative upper or lower limits. For example, if the range is 1.1 to 2.1, the following numbers 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and 2.0 can be selected as lower or upper limits.

[0026] In the examples set forth herein, concentrations, temperatures, and reaction conditions (e.g., pressure, pH, flow rates, etc.) can be practiced as set forth in the examples, or as modified in the improvements below, with the understanding that the values provided in the examples are to be rounded or truncated to two significant digits. In the improvements, concentrations, temperatures, and reaction conditions (e.g., pressure, pH, flow rates, etc.) can be practiced as set forth in the examples, or as modified in the improvements below, with the understanding that the values provided in the examples are to be rounded or truncated to two significant digits. In another improvement, concentrations, temperatures, and reaction conditions (e.g., pressure, pH, flow rates, etc.) can be practiced as set forth in the examples, or as modified in the improvements below, with the understanding that the values provided in the examples are to be rounded or truncated to two significant digits.

[0027] The term "and / or" as used herein refers to either all of the elements being present or only one of the elements being present. For example, "A and / or B" means "A alone, or B alone, or both A and B." In the case of "A alone," the term also encompasses the possibility of B not being present, i.e., "A alone, but no B."

[0028] It is also to be understood that the application is not limited to the particular implementation described herein, as specific components and / or conditions may, of course, vary. Further, the terminology used herein is for the purpose of describing particular embodiments of the application and is not intended to be limiting in any manner.

[0029] The terms "comprising," "including," "carrying," "having," "containing," or "characterized by" are synonymous and are used interchangeably. These terms are inclusive and open-ended and do not exclude additional, unrecited elements or method steps.

[0030] The phrase "consisting of" excludes any element, step, or ingredient not specified in the claim. When this phrase appears in a clause of the body of a claim, it acts as a discrete clauselimiter for that clause only. It does not exclude additional elements or steps not specified in the entire claim from being present.

[0031] The phrase "consisting essentially of" limits the scope of a claim to the specified materials or steps and to materials or steps that do not materially affect the basic and novel characteristic(s) of the claimed subject matter.

[0032] With respect to the terms "comprising," "consisting of," and "consisting essentially of," the presently disclosed and claimed subject matter can include the use of either of the other two terms, when one of the three terms is used herein.

[0033] The term "one or more of" means "at least one," and the term "at least one" means "one or more of." The terms "one or more of" and "at least one" include "a plurality of" as a subset.

[0034] A group or class of materials is described as suitable for the stated use for which an embodiment or embodiments are related. This means that a mixture of any two or more members of the group or class is suitable. Describing components by chemical terminology means the components as they exist when added to any combination specified in the specification, and does not necessarily exclude chemical interaction between components of the mixture once mixed. The first definition of a first letter acronym or other abbreviation applies to all subsequent uses of the same abbreviation herein and is intended to apply to normal grammatical variations of the originally defined abbreviation. Unless explicitly stated to the contrary, a measurement of a property is determined by the same technique referred to previously or subsequently for the same property.

[0035] When the capture agent is labeled with a redox tag molecule in solution, electrochemical detection of the redox molecule can be used for detection. According to current protocols, these electrochemical detection processes require washing of the solution or changing the solution. When the capture agent with the redox tag is present in a solution sample, the capture agent with the redox tag contributes to the electrical signal from the oxidation and reduction electrodes through redox reactions. When the redox tag is stable in its reduced form, oxidation makes the molecule active for signaling purposes. If the redox tag is stable in its oxidized form, reduction is the first step to get the signal. Some oxidized molecules can reach the other electrode and be reduced. Thus, oxidation and reduction currents can be measured from the first and second electrodes.

[0036] When the target molecule is added, if the target molecule is in pure buffer, a dilution effect will occur. To maintain the same concentration of redox tag molecules, the target molecule sample can be prepared using the same amount of redox tag molecules (e.g., a 1 : 1 mixture of target molecule and 2x redox tag labeled capture agent). Quantification can be considered with a dilution factor. When the target molecule is added, the target molecule forms a heavier complex with the capture agent, changing the diffusion rate. In this case, (1) free capture agent and (2) the bound complex of target molecule and capture agent provide two sources for redox signaling. Current protocols use interdigitated array electrodes to measure the diffusion coefficient of the molecules.

[0037] However, current protocols do not measure the redox current curves from both the oxidation electrode and the redox electrode when a voltage pulse (e.g., different voltage pulses) is applied to the oxidation electrode and the reduction electrode. It is desirable for a target molecule detection system and method in which redox current curves from voltage pulses (e.g., different voltage pulses) applied to the oxidation electrode and the reduction electrode are measured, and the redox current curves are indicative of the presence and / or amount of target molecules in the solution.

[0038] One or more embodiments disclose a method of detecting the presence of a target molecule when it binds to a capture agent. When the target molecule binds to the capture agent, one or more bound complexes are formed. The formation of the one or more bound complexes changes the diffusion behavior characteristics. The change in the diffusion behavior characteristics can be detected, thereby detecting the presence of the target molecule (e.g., DNA, protein, and small molecule).

[0039] One or more embodiments disclose a system of detecting the presence of a target molecule. The target molecule detection system includes first and second electrodes (e.g., oxidation electrode and reduction electrode). The first and second electrodes can be as a set. In one or more embodiments, the target molecule detection system can include multiple sets of electrode pairs, where each electrode pair can have different separation distances and / or different electrode designs.

[0040] The target molecule detection system can include a capture agent. The capture agent includes a redox tag configured to provide an electrochemical signal from the first and second electrodes. When the sample solution contains only the capture agent, an initial redox signal can serve as a baseline. After the addition of the target molecule to the sample solution, a binding complex is formed with at least one capture agent and at least one target molecule. The formation of the binding complex introduces a change in the diffusion behavior characteristics (e.g., a diffusion rate of the sample solution containing the target molecule). The change in the diffusion rate changes the redox current profile, which reflects the amount of the target molecule present in the sample molecule. In one or more embodiments, the detection system can operate without a washing step or solution change, as the detection is based on the change in the diffusion behavior characteristics of the capture agent.

[0041] One or more embodiments relate to a target molecule detection system and method for sensing a target molecule in a solution phase by measuring an electrical parameter of an electrochemical redox signal to determine a change in diffusion rate. The change in diffusion rate can be used to detect the presence of the target molecule.

[0042] Figure 1 A schematic of an electrochemical detection system 10 is depicted having an oxidation electrode 12, a reduction electrode 14, and a passivation layer 18. In one or more embodiments, the passivation layer 18 is configured to protect the oxidation electrode 12 and the reduction electrode 14 from corrosion or oxidation and to define an active portion of the electrodes, which can improve accuracy. The oxidation electrode 12 can be referred to as Ml and the reduction electrode 14 can be referred to as M2. The oxidation electrode 12 and the reduction electrode 14 can be formed from platinum, gold, any conductive indium tin oxide (ITO) material, and metal oxides. The oxidation and reduction electrodes 12 and 14 are spaced apart from each other by a spacer region 16 such that the oxidation and reduction electrodes 12 and 14 do not contact each other. The oxidation electrode 12 includes a lead portion 24 connected to a power source and a sensing portion 26 having a curved thickness. The reduction electrode 14 includes a lead portion 20 connected to a power source and a sensing portion 22 having a solid curved region. As shown in FIG. 1, the sensing portion 22 of the reduction electrode 14 partially surrounds the sensing portion 26 of the oxidation electrode 12 and is spaced apart therefrom by the spacer region 16. Figure 1 As shown in FIG. 1, the sensing portion 22 of the reduction electrode 14 partially surrounds the sensing portion 26 of the oxidation electrode 12 and is spaced apart therefrom by the spacer region 16.

[0043] The oxidation and reduction electrodes 12 and 14 can be formed of a flexible material. The type of flexible material can be selected such that the spacing region 16 remains fixed and the area of each of the oxidation and reduction electrodes 12 and 14 remains constant. The area of each of the oxidation and reduction electrodes can be in the nanometer scale to centimeter, and in some embodiments, in the micrometer range. The oxidation and reduction electrodes 12 and 14 can be separated by a fixed distance. The fixed distance of each of the oxidation and reduction electrodes can be in the nanometer scale to centimeter, and in some embodiments, in the micrometer range. In one or more embodiments, the type of flexible material is selected such that the material remains stable under multiple rounds of electrochemical measurements.

[0044] As shown in FIG. 1, the electrochemical detection system 10 includes a volume of solution. The solution can be composed of any biological buffer solution. The electrochemical detection system 10 can form a diffusion-based, no-wash sensing mechanism. The solution includes redox labels 28, represented by stars, and capture agents 30, represented by curved sections. Figure 1 As shown in FIG. 2, the redox labels 28 bind to the capture agents 30. Figure 1

[0045] Figure 2A A schematic diagram depicting the reaction and diffusion mechanism of the redox labels 28 in the electrochemical detection system 10 is depicted. As depicted by a first arrow 32, the redox labels 28 in the reduced state change to the oxidized state at the oxidation electrode 12. As depicted by a second arrow 34, the redox labels 28 in the oxidized state diffuse to the reduction electrode 14 at the oxidation electrode 12. At the reduction electrode 14, the redox labels 28 in the oxidized state change to the reduced state as shown by a third arrow 36.

[0046] Figure 2B A graph 50 depicting the oxidation voltage pulse 52 applied to the oxidation electrode 12 (Ml) and the oxidation potential 54 of the oxidation electrode 12 is depicted. Figure 2C A graph 56 depicting the reduction voltage pulse 58 applied to the reduction electrode 14 (M2) and the reduction potential 60 of the reduction electrode 14 is depicted. Figure 2D A graph 62 depicting the oxidation current curve 64 at the oxidation electrode 12 in response to the oxidation voltage pulse 52 is depicted. Figure 2E A graph 66 depicting the reduction current curve 68 at the reduction electrode 14 in response to the reduction voltage pulse 58 is depicted. Figures 2B to 2E A schematic diagram of a baseline current measurement according to one embodiment is collectively provided.

[0047] As shown in FIG. 1, the electrochemical detection system 10 includes a volume of solution. The solution can be composed of any biological buffer solution. The electrochemical detection system 10 can form a diffusion-based, no-wash sensing mechanism. The solution includes redox labels 28, represented by stars, and capture agents 30, represented by curved sections. Figure 2B and 2C ​As shown, different potentials (i.e., oxidation potential and reduction potential, respectively) are applied to the oxidation electrode 12 and the reduction electrode 14. A known concentration (e.g., 10 to 100 mmol to picomolar range) of the trapping agent is placed in a solution containing redox-tagged molecules. In one case, the redox-tagged molecules may be in a reduced state. In this case, the trapping agent first interacts with the oxidation electrode 12 where the redox tag is oxidized, thereby generating an oxidation current through the oxidation electrode 12. The oxidation current is measured and can be plotted, for example, as shown. Figure 2D As shown in the diagram, some of the oxidized redox tags of the trapping agent diffuse to the reduction electrode 14. Some of these oxidized redox tags are reduced at the reduction electrode 14, thereby inducing a redox current at the reduction electrode 14. The redox current at the reduction electrode 14 is measured and can be plotted, for example, as shown in the diagram. Figure 2E As shown in the figure. The time delay between the start of the oxidation current and the start of the reduction current (e.g.) Figure 2D and 2E Δt in b (As shown in Figure 70) is related to the diffusion rate of the trapping agent. Since the current has only one source (i.e., the trapping agent), the current curve serves as a baseline signal in a relatively simple form. One or more electrical parameters can be used to characterize... Figure 2D and 2E The response is shown in the figure. As mentioned above, one of the electrical parameters can be the time delay (Δt). b Other parameters may include the level of oxidation current at equilibrium (e.g., Figure 2D I in ox_b (as shown) and the reduction current level at equilibrium (as shown) Figure 2E I in rx_b (As shown).

[0048] One or more parameters of the electrochemical detection system 10 can be optimized to achieve high sensitivity and / or selectivity. These parameters may include the area of ​​the oxidation electrode 12 and / or the reduction electrode 14, the distance between the oxidation electrodes and / or the oxidation electrodes 14, the viscosity of the solution, and the concentration of the trapping agent.

[0049] Figure 3A A schematic diagram depicts the reaction and diffusion mechanism of the redox tag 28 in the electrochemical detection system 10, where the target molecule 82 is added to the solution. As depicted by the first arrow 80, the redox tag 28, in a reduced state, changes to an oxidized state at the oxidation electrode 12. Figure 3AAs shown, the trapping agent 30 and the target molecule 82 bind to the redox tag 28. As depicted by the second arrow 84, the redox tag 28 in the oxidized state diffuses from the oxidation electrode 12 to the reduction electrode 14. At the reduction electrode 14, the redox tag 28 in the oxidized state is changed to the reduced state as shown by the third arrow 86.

[0050] Figure 3B Figure 90 depicts the oxidation voltage pulse 92 applied to the oxidation electrode 12 (M1) and the oxidation potential 94 of the oxidation electrode 12. Figure 3C Figure 96 depicts the reduction voltage pulse 98 applied to the reduction electrode 14 (M2) and the reduction potential 100 of the reduction electrode 14. Figure 3D Figure 102 depicts the oxidation current curve 104 at the oxidation electrode 12 in response to the oxidation voltage pulse 92. Figure 3D The baseline oxidation current measurements (i.e., oxidation current curve 64) were also depicted. Figure 3E Figure 106 depicts the reduction current curve 108 at the reduction electrode 14 in response to the reduction voltage pulse 98. Figure 3E The baseline restoration current measurement (i.e., restoration current curve 68) was also depicted.

[0051] When target molecule 82 is added to the solution, some of the trapping agent 30 binds to target molecule 82, thereby reducing the diffusion rate between oxidation electrode 12 and reduction electrode 14. In this case, as... Figures 2A to 2E As shown, the same procedure used for baseline signal detection can be used to detect changes introduced by the target molecule. In this case, there is a mixed population of unbound trapping agent and target-trapping complexes. Compared to the baseline measurement, the mixed population increases the complexity of the current response. In this case, the current initiation introduced by the unbound trapping agent has the same time delay as the baseline measurement, but the current magnitude is smaller due to the reduced concentration. The bound complexes contribute to a second initiation of the current, which occurs with a time delay (e.g., ...). Figure 3D and 3E Δt in s (As shown in Figure 110). One or more electrical parameters can be used to characterize... Figure 3D and 3E The response is shown in the figure. As mentioned above, one of the electrical parameters can be the time delay (Δt). s Other parameters may include the level of oxidation current at equilibrium (e.g., Figure 3D I in ox_s (as shown) and the reduction current level at equilibrium (as shown) Figure 3E I in rx_s (As shown). In one or more implementations, Δt s and Δt b I ox_s and Iox_b and / or I rx_s and I rx_b The difference between and / or I

[0052] The sensing mechanism of the electrochemical detection system of one or more embodiments depends on the change in diffusion rate. It is beneficial in these embodiments to minimize interference in the sample solution containing the target molecule. One embodiment to minimize interference is to limit the measurement volume of the electrochemical detection system.

[0053] Figure 4A A schematic diagram of an electrochemical detection system 150 is depicted, including a microchannel 152 partially enclosed by a first valve 154 and a second valve 156 connected thereto. The microchannel 152 is configured to contain a relatively small volume of sample solution (e.g., in the picoliter range, nanoliter range, or microliter range). The relatively small volume of sample solution increases sensitivity because there is a higher likelihood that the target molecule will interact with both the oxidizing electrode 158 and the reducing electrode 160 during multiple rounds of measurement. The first valve 154 and the second valve 156 are configured to confine the sample solution in the microchannel 152 to minimize interference in the sample solution.

[0054] Figure 4B A schematic representative view of an electrochemical detection system 200 is depicted, including a base 202 and a microwell array 204 extending into the base 202. Figure 4C An enlarged view of a microwell 206 in the microwell array 204 is depicted. As shown in Figure 4B The microwell is cylindrical. The microwell structure is configured to increase the residence time of molecules therein within a relatively small volume. In one or more embodiments, the opening 208 of the microwell 204 can have a mechanical lid and / or be covered by an immiscible liquid (e.g., oil). As shown in Figure 4B The oxidizing electrode 210 and the reducing electrode 212 are arranged to contact the interior volume of the microwell 206. The oxidizing electrode 210 and the reducing electrode 212 are spaced apart from each other by a fixed distance. The reducing electrode 212 is spaced apart from the bottom of the microwell 206 by a fixed distance. The oxidizing electrode 210 is spaced apart from the opening of the microwell 206 by a fixed distance. The oxidizing electrode 210 is closer to the opening of the microwell 206 than the reducing electrode 212. In an alternative embodiment, the reducing electrode 212 is closer to the opening of the microwell 206 than the oxidizing electrode 210. The oxidizing electrode 210 includes a base 214 having a profile (e.g., a circular profile as shown in Figure 4C The inner surface of the base 214 contacts the solution within the microwell 206. The lead 216 is connected to a power source. The reducing electrode 212 includes a base 218 having a profile (e.g., a circular profile as shown inFigure 4C Figure 4C The base 218 has a circular profile (as shown in the cross-sectional view of FIG. 2B) and leads 220 extending from the base 218. An inner surface portion of the base 218 is in contact with the solution within the microwell 206. The leads 220 are connected to a power source.

[0055] The processes, methods, or algorithms disclosed herein (e.g., detecting a target molecule in response to one or more electrical properties of first and second oxidation current profiles and first and second reduction current profiles) can be embodied in, and fully automated via, software and / or code modules executed by a processing device, controller, or computer. As such, the processes, methods, or algorithms can be stored on and / or transmitted across some transmission medium and executed by a processor. The processes, methods, or algorithms can also be embodied in some tangible computer-readable medium for execution by a processor, such as a floppy diskette, a CD-ROM, a hard drive, a USB flash drive, or a solid state drive. Each of these media types can have different associated data storage capacities and each type of media can have different access times. The examples described herein are merely exemplary and are not intended to limit the scope of the disclosure. The processes, methods, or algorithms described herein can be implemented in a distributed manner via, e.g., cloud computing. Each process, method, or algorithm can be stored in a computer program product, which can be implemented in a machine-readable medium, which can be a computer-readable storage medium or memory, which can include any suitable data storage device. The computer program product can also be distributed over a network, for example, via a server from a manufacturer, a device manufacturer, or a third party maintenance and service provider. The computer program product can be accessible via the network and a remote application executed by a processor can access the computer program product and automatically download portions of the computer program product to a device as needed.

[0056] While the foregoing describes exemplary embodiments, these embodiments are not meant to describe all possible forms of the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure. As previously described, features of various embodiments can be combined to form further embodiments of the present disclosure not explicitly described or illustrated. While various embodiments can have been described as providing advantages or being preferred over other embodiments or prior art implementations, one of ordinary skill in the art will recognize that a variety of components and / or features can be substituted for those described or claimed, and that many implementations of the present disclosure have different or additional advantages. As such, the foregoing description is not intended to be construed in a limiting sense, and the description is provided to illustrate and enable the various embodiments of the present disclosure.

Claims

1. A target molecule detection system, comprising: A chamber configured to contain a solution having a redox tag and a scavenger bound to the redox tag, the redox tag being present in the solution in a reduced and / or oxidized state, the scavenger being configured to bind to a target molecule introduced into the solution; An oxidation electrode is configured to oxidize a redox tag present in the solution in a reduced state to an oxidized state. When the solution does not contain the target molecule, the oxidation electrode is configured to output a first oxidation current curve in response to a first oxidation voltage pulse applied to the oxidation electrode. When the solution contains the target molecule, the oxidation electrode is configured to output a second oxidation current curve in response to a second oxidation voltage pulse applied to the oxidation electrode. and A reduction electrode, spaced apart from the oxidation electrode, is configured to reduce a redox tag present in the solution in an oxidized state to a reduced state. When the solution does not contain the target molecule, the reduction electrode is configured to output a first reduction current curve in response to a first reduction voltage pulse applied to the reduction electrode. When the solution contains the target molecule, the reduction electrode is configured to output a second reduction current curve in response to a second reduction voltage pulse applied to the reduction electrode. One or more electrical properties of the first and second oxidation current curves and the first and second reduction current curves indicate the presence of the target molecule.

2. The target molecule detection system according to claim 1, wherein when the redox tag is stable in a reduced state as an initial state, the signal transduction process is configured to start from the oxidation electrode, and when the redox tag is stable in an oxidized state as an initial state, the signal transduction process is configured to start from the reduction electrode.

3. The target molecule detection system according to claim 1, wherein the first and second oxidation voltage pulses are equal, and the first and second reduction voltage pulses are equal, and the first and second oxidation pulses are different from the first and second reduction pulses.

4. The target molecule detection system according to claim 1, wherein the first and second oxidation voltage pulses are greater than the oxidation potential of the redox tag molecule.

5. The target molecule detection system according to claim 1, wherein the first and second reduction voltage pulses are less than the reduction potential of the redox tag molecule.

6. The target molecule detection system according to claim 1, wherein the oxidation electrode and the reduction electrode are spaced apart by a fixed distance.

7. The target molecule detection system according to claim 1, wherein one or more electrical properties of the first and second oxidation current curves include time-delayed initiation oxidation current and steady-state oxidation current levels.

8. The target molecule detection system according to claim 1, wherein one or more electrical properties of the first and second reduction current curves include a time-delayed initial reduction current and a steady-state reduction current level.

9. The target molecule detection system of claim 1, wherein when the solution does not contain the target molecule, the solution has a first redox tag concentration, and when the solution contains the target molecule, the solution has a second redox tag concentration, and the first and second redox tag concentrations are equal.

10. The target molecule detection system of claim 1, wherein one or more electrical properties of the first and second oxidation current curves and the first and second reduction current curves indicate the amount of the target molecule.

11. A method for detecting a target molecule, comprising: An oxidation electrode and a reduction electrode are contacted with a solution having a redox tag and a trapping agent bound to the redox tag, the redox tag being present in the solution in a reduced and / or oxidized state, and the trapping agent being configured to bind to a target molecule introduced into the solution; When the solution does not contain the target molecule, a first oxidation voltage pulse is applied to the oxidation electrode to obtain a first oxidation current curve; When the solution contains the target molecule, a second oxidation voltage pulse is applied to the oxidation electrode to obtain a second oxidation current curve; When the solution does not contain the target molecule, a first reduction voltage pulse is applied to the reduction electrode to obtain a first reduction current curve; When the solution contains the target molecule, a second reduction voltage pulse is applied to the reduction electrode to obtain a second reduction current curve; and The target molecule is detected in response to one or more electrical properties of the first and second oxidation current curves and the first and second reduction current curves.

12. The target molecule detection method according to claim 11, wherein when the redox tag is stable in a reduced state as an initial state, the signal transduction process is configured to start from the oxidation electrode, and when the redox tag is stable in an oxidized state as an initial state, the signal transduction process is configured to start from the reduction electrode.

13. The target molecule detection method according to claim 11, wherein the first and second oxidation voltage pulses are equal, and the first and second reduction voltage pulses are equal, and the first and second oxidation pulses are different from the first and second reduction pulses.

14. The target molecule detection method according to claim 11, wherein the first and second oxidation voltage pulses are greater than the oxidation potential of the redox tag molecule.

15. The target molecule detection method according to claim 14, wherein the first and second reduction voltage pulses are less than the reduction potential of the redox tag molecule.

16. The target molecule detection method according to claim 15, wherein the oxidation potential of the redox tag molecule is greater than the reduction potential of the redox tag molecule.

17. The target molecule detection method according to claim 15, further comprising maintaining a redox tag concentration when the solution does not contain the target molecule and when the solution contains the target molecule.

18. The target molecule detection method according to claim 15, further comprising deconvolving the first and second oxidation current curves and the first and second reduction current curves to obtain the amount of the target molecule.

19. The target molecule detection method according to claim 11, wherein the first, second, third and fourth application steps are performed without changing the solution or cleaning the oxidation electrode or the reduction electrode.

20. A method for detecting a target molecule, comprising: An oxidation electrode and a reduction electrode are contacted with a solution having a redox tag and a trapping agent bound to the redox tag, the redox tag being present in the solution in a reduced and / or oxidized state, and the trapping agent being configured to bind to a target molecule introduced into the solution; When the solution does not contain the target molecule, a first oxidation voltage pulse is applied to the oxidation electrode to obtain a first oxidation current curve; When the solution contains the target molecule, a second oxidation voltage pulse is applied to the oxidation electrode to obtain a second oxidation current curve; When the solution does not contain the target molecule, a first reduction voltage pulse is applied to the reduction electrode to obtain a first reduction current curve; When the solution contains the target molecule, a second reduction voltage pulse is applied to the reduction electrode to obtain a second reduction current curve; and The target molecule is detected in response to a first difference between the first and second oxidation current curves and / or a second difference between the first and second reduction current curves.

21. The target molecule detection method according to claim 20, wherein when the redox tag is stable in a reduced state as an initial state, the signal transduction process is configured to start from the oxidation electrode, and when the redox tag is stable in an oxidized state as an initial state, the signal transduction process is configured to start from the reduction electrode.

22. The target molecule detection method of claim 20, wherein the detection step includes detecting the target molecule in response to a first difference between the first and second oxidation current curves and / or a second difference between the first and second reduction current curves.

23. The method for detecting a target molecule according to claim 20, wherein the oxidation electrode and the reduction electrode comprise a first electrode pair and a second electrode pair, and further comprises repeating the first, second, third, and fourth application steps on each of the first electrode pair and the second electrode pair.

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